1. Field of the Invention
The present invention is in the field of silicone and siloxane chemistry. More particularly, the present invention relates to a process for preparing diphenyl-dialkoxysilane and phenylalkyl-dialkoxysilane compounds which have their primary use in the preparation of octaphenylcyclotetrasiloxane and sym-tetraalkyltetraphenyl-cyclotetrasiloxane compounds.
2. Brief Description of the Prior Art
Octaphenylcyclotetrasiloxane and sym-tetraalkyltetraphenyl-cyclotetrasiloxane compounds are important raw or starting materials for the preparation of various siloxane containing products. U.S. Pat. No. 5,739,370 discloses a process for preparing these compounds, in which diphenyldimethoxysilane and methylphenyldimethoxysilane are converted into octaphenylcyclotetrasiloxane and sym-tetraalkyltetraphenyl-cyclotetrasiloxane, respectively. In accordance with this prior art patent, the intermediates diphenyldimethoxysilane and methylphenyldimethoxysilane are obtained by alcoholysis from the corresponding halogenated silanes, that is from dihalodiphenylsilane, and from dihalomethylphenylsilane, respectively. However, the handling of halogenated silane compounds, such as of the dihalodiphenylsilanes, and dihalomethylphenylsilanes in the process of this prior art patent, has several disadvantages, because the halogenated silanes react with atmospheric moisture to produce toxic and corrosive acids (such as hydrogen chloride) and are, generally speaking, difficult to handle. Therefore, there is a need in the art for a process of synthesizing octaphenylcyclotetrasiloxane and sym-tetraalkyltetraphenyl-cyclotetrasiloxane compounds without using halogenated silanes as the starting materials. More specifically stated, there is a need in the art for synthesizing diphenyldialkoxysilanes and methylphenyldialkoxysilanes as intermediates for the synthesis of octaphenylcyclotetrasiloxane and sym-tetraalkyltetraphenyl-cyclotetrasiloxane compounds while avoiding the use of halogenated silanes in the process.